EULAMELLIIM'IANCHIATA TELLINACEA 



453 



branchial orifice on the buccal margin, foot long-, broadened, with 



a byssns, animal usually viviparous. Tertiary . Genera : 



Erycina, Kellia, Pytliina, Lasaea,Lepton. 



Fam. 15. Galeommidae. — Mantle edges more or less reflected 

 over the shell, apertures and foot as in Erycinidae ; shell thin, 



equilateral, hinge with few teeth or none. Tertiary . 



Genera : Galeomma, Scintilla, SporteUa, Chlamydoconcha, Hinds- 

 iella, Ephippodonta (Fig. 32, p. 81). 



Fam. 1 6. Cyrenidae. — Siphons short, foot large, no byssus ; 

 shell equivalve, subtriangular, with periostracum, hinge with two 

 or three cardinals, laterals present ; animal hermaphrodite, 



viviparous. Fresh or brackish water. Jurassic . Genera : 



Cyrena, Corhicula (subg. Batissa, Vclorita), Sp)haerin,rii ( = Cyehis), 

 Pisidiitm, Galatea, Fischeria. 



The families Cyrenellidae (single genus Cyrenella) and 

 Baufiiidae (single genus Bangia) are probably to be placed here. 



Sub-order II. Tellinacea. — Siphons long, separate, foot and 

 labial palps very large, pallial sinus deep, two adductor muscles. 



Fam. 1. Tellinidae. — External branchial fold directed dorsally, 

 foot with byssogenous slit, but no byssus, branchiae small ; shell 

 compressed, equivalve, ligament external, at least two cardinals 



in each valve, laterals variable. Cretaceous . Principal 



genera : Tdl'ina (with many sections), Gastrana. 



Fam. 2. Scrobictdariidae. — Animal as in Tcllina ; shell orbicu- 

 late or long oval, equivalve, 

 hinge teeth weak, liga- 

 ^ ment in an internal cavity. 

 Tertiary . Prin- 



cipal genera : Scrohieu- 

 laria, Syndosmya, Tlieora , 

 Cuminfjia, Semde. 



Fa jr. 3. Donacidae. — 

 External branchial fold 

 directed ventrally ; shell 

 equivalve, subtriangular, solid, smooth, two or three cardinals in 



each valve, laterals variable, ligament external. Jurassic . 



Genera ; Donax, Iphigenia, Isodonta. 



Fam. 4. Tancrediidae. — Shell donaciform, ligament external, 

 cardinals usually two in each valve, posterior laterals strong. 

 Trias . Genera : Tancredia (Secondary strata), Hemidonax. 



Fig. S06.—Teni7ia rasfeUi'm Hani., East Indies. 



